Two-phase projectile with a proximal compression chamber

ABSTRACT

A man-powered system for pneumatically launching a pellet cluster includes a cartridge for holding the pellet cluster. A hollow propulsion shaft receives the cartridge for substantially free travel back and forth in the shaft to establish a variable-volume compression chamber in the shaft, between the cartridge and a closed end of the shaft. When a driving force acts to launch the combination of cartridge and shaft, the cartridge moves to compress gas in the compression chamber for a subsequent expansion that will propel the cartridge forward through the shaft. After launch, the compressed gas acts to separate the pellet cluster from the cartridge and to provide a pneumatic assist that increases the velocity of pellets after separation.

This application is a continuation-in-part of application Ser. No. 13/789,514, filed Mar. 7, 2013, which is currently pending. The contents of application Ser. No. 13/789,514 are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains generally to man-powered devices for launching pellet clusters. More particularly, the present invention pertains to man-powered launchers that provide a pneumatic assist to pellets as they are being launched. The present invention is particularly, but not exclusively, useful as a man-powered device that provides, in combination, a cartridge for holding a pellet cluster and a propulsion tube for interacting with the cartridge to create compressed gas during a launch, to thereby provide a pneumatic assist for increasing the velocity for the pellets after they become separated from the cartridge.

BACKGROUND OF THE INVENTION

An important factor for evaluating the performance of a man-powered launcher is the velocity at which a projectile is released from the launcher. Regardless whether the projectile is an arrow, a bolt, or a shot cluster, and regardless whether the projectile is launched by either a vertical bow or a crossbow, the resultant projectile velocity is an important measure of the launcher's performance. In the event, the resultant projectile velocity will be a function of the amount of energy (i.e. the capacity to perform work) that can be stored in the launcher prior to projectile launch, and thereafter used to propel the projectile onto its flight path. For the specific case of a man-powered weapon, a contributing factor for performance is the physical ability of the user.

In general, energy can be classified as being either thermal energy, potential energy or kinetic energy. Of primary interest here are potential and kinetic energy. By definition, potential energy is the energy which is possessed by a body by virtue of its position or condition relative to other bodies. For example, an object weighing one pound, when positioned ten feet above a surface prior to being dropped onto the surface, will expend ten foot-pounds of energy when it impacts against the surface. In this example, by virtue of its position relative to the surface, the one pound object had a potential energy of ten foot-pounds. As another example of potential energy, a compressed gas has a potential energy for performing work as it is allowed to expand. On the other hand, unlike potential energy, kinetic energy is the energy (work capacity) that a body possesses by virtue of being in motion. Mathematically expressed, kinetic energy is a function of the velocity of the object. Specifically, a particle having a mass “m”, that is moving with a linear velocity “v”, has a kinetic energy that is mathematically expressed as “½ mv²”. As is well known, potential energy and kinetic energy are interchangeable.

In light of the above, it is an object of the present invention to provide a device and method for converting the potential energy of a launching device into the potential energy of a compressed gas inside the projectile during a launch of the projectile; and then transferring this potential energy to a payload for use as kinetic energy that will increase velocity of the payload after the initial launch. Another object of the present invention is to provide a device and method for launching a projectile to achieve an in-flight velocity that otherwise exceeds the capability of the launching device. Yet another object of the present invention is to provide a device and method for launching a pellet cluster from a man-powered launcher. Still another object of the present invention is to provide a device and method for launching projectiles with a pneumatically assisted operational velocity that is easy to use, is simple to implement and is comparatively cost effective.

SUMMARY OF THE INVENTION

In accordance with the present invention, a device and method are provided for launching a projectile from a man-powered device which will achieve an in-flight velocity that otherwise exceeds the capability of the launching device by itself. More specifically, in an energy transfer sequence, the potential energy that is initially established in the projectile launcher is converted into kinetic energy for the projectile as the projectile is launched onto its flight path. Next, the kinetic energy that is imparted to the projectile is then, at least in part, converted into potential energy by compressing gas in a chamber, inside the projectile. In turn, this potential energy is transferred to a payload, as the compressed gas is allowed to expand, for use as kinetic energy that will increase payload velocity after the initial launch. Note that this multistep energy conversion process occurs in a dynamic fashion, such that various steps of the process may overlap in time.

Structurally, a device for the present invention includes a first component that is tubular shaped and is formed with a lumen which defines an axis. Further, the first component has an open end and a closed end. Also included in the device of the present invention is a second component that is engaged with the first component to create an assembly. Specifically, this assembly establishes a gas-filled compression chamber in the lumen of the first component that is located between the second component and the closed end of the first component. Within this combination, the assembly allows for a substantially free axial movement of the second component back and forth in the compression chamber of the assembly. Further, depending on the embodiment of the present invention, a payload is selectively mounted on a component of the assembly. For the present invention, the payload may be either a conventional arrow (e.g. a broadhead) as used with a vertical bow (launcher), a bolt as used with a crossbow (launcher), or a shot cluster that may be adapted for use by either type launcher.

As envisioned for the present invention, a man-powered launcher will be used to generate an axially-directed driving force on one component of the assembly (projectile) in order to propel the projectile from the launcher and onto its flight path. A consequence of this driving force is to cause a relative movement between the first component and the second component. Recall, the second component is free to move within the lumen of the first component (i.e. it is free to move within the gas chamber of the assembly). In the event, this movement further compresses gas in the compression chamber to thereby increase potential energy in the compressed gas.

Once gas in the compression chamber has been compressed as much as possible, which occurs at or about the time when the driving force becomes zero, the gas then begins to expand. During this expansion, potential energy in the gas is converted to kinetic energy by equal and opposite forces to both the first and second components. This causes a resultant increase in the velocity of one component, and a resultant dissipation in the velocity of the other component; a combination of events that separates the payload from the assembly.

With the above in mind, the present invention envisions two different types of operational embodiments. In one, the payload is mounted on the second component, and the driving force is generated on the first component. In the other embodiment, the payload is mounted on the first component and the driving force is generated on the second component. In either embodiment, the mass of the proximal (i.e. aft) component (m_(p)) can be less than the mass of the distal (i.e. forward) component (m_(d)). For both embodiments, the driving force for launch is exerted against the proximal component.

For an operation of the present invention, a launcher is selected and is configured (i.e. armed) for launch. Stated differently, the launcher is configured to store potential energy. A projectile is then positioned on the launcher for launch. Upon firing the launcher, the potential energy that is stored in the launcher is converted to kinetic energy by way of the driving force that acts to propel the projectile from the launcher. Specifically, this driving force acts on the projectile and is directed to accelerate the projectile along an axial path that is defined by the projectile.

During the initial acceleration of the projectile by the driving force, a first kinetic energy is generated for the first component of the assembly, and a second kinetic energy is generated for the second component of the assembly. All of this happens for separate but interrelated reasons. Specifically, the different components of the assembly will preferably be of different mass, and they can have different velocities at launch (recall: kinetic energy equals ½ mv²). In more detail, the different velocities occur because, while the driving force acts directly on the first component to accelerate it along the flight path, the second component experiences no such direct force. Instead, the second component tends to remain at rest and is accelerated only by forces exerted on it by the gas which is compressed in the compression chamber.

Simultaneously, as kinetic energy is imparted to the first and second components of the assembly, a potential energy is stored within the gas in the gas-filled chamber of the assembly. Specifically, this increase in potential energy occurs because the second component moves toward the first component during the initial acceleration, and the gas is compressed between components as the gas chamber is diminished in size. At the end of the first component's initial acceleration, the gas has been compressed as much as possible and it has its highest potential energy.

After the initial acceleration of the projectile (i.e. when the driving force becomes zero), the potential energy of the gas is converted into kinetic energy and an expansion of the gas acts on both the first component and the second component. The result here is an additional acceleration of the second component and its payload for separation of the payload from the projectile (assembly), and by a deceleration of the remainder of the projectile.

In an adaptation of the present invention, a projectile assembly is provided for pneumatically launching a pellet cluster from a man-powered launcher. In combination, as indicated above, the projectile assembly includes a cartridge for holding the pellet cluster and a hollow propulsion shaft for receiving the cartridge in its lumen. In this combination, the cartridge and the propulsion shaft interact with each other to generate additional pneumatic potential energy that will launch the pellet cluster at an increased velocity from the cartridge. Pellets in the pellet cluster are preferably made of a material such as tungsten or steel.

In detail, the elongated tubular-shaped cartridge (sabot) of the projectile assembly has an open distal end and a closed proximal end. Further, the cartridge includes a retention groove which is formed at its proximal end, and it has an O-ring assembly that is positioned in the retention groove to establish a substantially airtight seal between the proximal end of the cartridge and an inner sidewall of the propulsion shaft.

Structurally, the O-ring assembly includes an outer ring that is positioned in the retention groove for direct contact with an inner surface of the propulsion shaft. Preferably, the outer ring is made of polytetrafluoroethylene (PTFE), and it is formed with a diagonal split that allows for expansion and contraction of the outer ring. The O-ring assembly also has an inner ring that is made of rubber and is positioned in the retention groove to produce a force against the outer ring that urges the outer ring into contact against the inner surface of the propulsion shaft. Further, the retention groove is formed with at least one vent hole to equalize pressure between the retention groove and the compression chamber during a launch of the pellet cluster.

Also included with the cartridge of the present invention is a retainer that is positioned in the lumen of the cartridge at its distal end. Specifically, the purpose of the retainer is to maintain the pellet cluster in the lumen of the cartridge prior to launch. Preferably, the retainer is a plurality of light weight tubes.

Additionally, the cartridge includes a friction collar that is positioned in a snug engagement against the outer surface of the cartridge. The purpose of this friction collar is to generate friction forces against the cartridge that will retard movement of the cartridge during the separation of the pellet cluster from the cartridge. In particular, the friction collar is preferably made of aluminum and it will exert a radial pressure against the cartridge of approximately 500 psi. Further, a slide ring assembly is positioned on the outer surface of the cartridge, distal to the friction collar. The purpose here is to mitigate impact forces against the friction collar at the launch of the pellet cluster.

For its structural cooperation with the cartridge of the present invention, the elongated, cylindrical-shaped propulsion shaft is dimensioned to receive the cartridge for substantially free travel back and forth in the lumen of the shaft. As previously disclosed, the propulsion shaft has a closed proximal end. Thus, the propulsion shaft interacts with the cartridge to establish a compression chamber in the lumen of the shaft between the closed proximal end of the cartridge and the closed proximal end of the propulsion shaft. As also previously disclosed, the volume of this compression chamber will change in response to movements of the cartridge back and forth in the shaft.

The propulsion shaft further includes a pressure valve that is positioned at the proximal end of the propulsion shaft. As envisioned for the present invention, the pressure valve will be mounted in a nock, and the nock will be affixed to the proximal end of the propulsion shaft for operational interaction with the launcher of the projectile assembly. Specifically, the purpose of the pressure valve is to allow the compression chamber to be pressurized to a predetermined gauge pressure (e.g. 80 psig) prior to imparting the driving force against the shaft, to thereby provide an initial level of resistance to the compression of gas in the compression chamber.

As an added feature for the projectile assembly, a ferrule is attached to the distal end of the propulsion shaft. In particular, the ferrule has a threaded extension projecting in a distal direction from the distal end of the shaft. A plug can then be joined in a threaded engagement with the ferrule to create an abutment around the open distal end of the propulsion shaft. This abutment then establishes a distal limit for movement of the cartridge in the lumen of the shaft. Also, because the plug is in a threaded engagement with the propulsion shaft, it can be easily removed for the replacement of a spent cartridge.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which

FIG. 1A is an elevation view of a projectile in accordance with the present invention, shown mounted on a vertical cross bow for launch;

FIG. 1B is a view of the projectile as shown in FIG. 1A with the projectile at the release point where it is launched from the launcher;

FIG. 1C is a view of the projectile as shown in FIGS. 1A and 1B with the payload in flight toward a target after the payload has separated from the remainder of the projectile;

FIG. 2 is a side view of a first preferred embodiment of a projectile in accordance with the present invention;

FIG. 3 is a side view of an alternate second preferred embodiment of a projectile in accordance with the present invention;

FIG. 4A is a cross section view of a first preferred embodiment of the projectile of the present invention as seen along the line 4-4 in FIG. 2, prior to a launch of the projectile;

FIG. 4B is a cross section view of the first preferred embodiment of the projectile as seen in FIG. 4A, at its release point, as it is being launched from the launcher;

FIG. 4C is a cross section view of the first preferred embodiment of the projectile as seen in FIGS. 4A and 4B, after a payload has been separated from the remainder of the projectile;

FIG. 5A is a cross section view of a second preferred embodiment of the projectile of the present invention as seen along the line 5-5 in FIG. 3, prior to a launch of the projectile;

FIG. 5B is a cross section view of the second preferred embodiment of the projectile as seen in FIG. 5A at its release point, as it is being launched from the launcher;

FIG. 5C is a cross section view of the second preferred embodiment of the projectile as seen in FIGS. 5A and 5B after a payload has been separated from the remainder of the projectile;

FIG. 6A is a perspective view of a projectile assembly in accordance with the present invention with a cartridge (shown in phantom) positioned inside a propulsion shaft and ready for launch (see FIG. 1A);

FIG. 6B is a view of the projectile assembly shown in FIG. 1A with the cartridge positioned inside the propulsion shaft after the assembly has been accelerated by a driving force (see FIG. 1B);

FIG. 7 is a side elevation view of a cartridge in accordance with the present invention; and

FIG. 8 is a cross section view of the projectile assembly as seen along the line 8-8 in FIG. 6A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1A, a device in accordance with the present invention is shown and is generally designated 10. As shown, the device 10 includes a projectile 12 and a man-powered launcher 14. In the particular case of the device 10 that is shown in FIG. 1A, the launcher 14 is a vertical bow of a type well known in the art. The launcher 14, however, could as well be a crossbow (not shown) or an air gun (not shown), both of which are of types well known in the pertinent art.

As illustrated sequentially in FIGS. 1A, 1B and 1C, a purpose of the present invention is to use the launcher 14 to propel the projectile 12 along a flight path (dashed line) 16 toward a target 18. In sequence, FIG. 1A shows the launcher 14 in a configuration for firing the projectile 12. FIG. 1B then shows the projectile 12 as it is being released from the launcher 14. And, FIG. 1C shows the projectile 12, and its payload 20 after it has been separated from the projectile 12 in flight, after launch. In particular, FIG. 1C shows that shortly after launch, the payload 20 continues along the flight path 16 toward the target 18, while the projectile 12, itself, falls to the ground along a separation path (dotted line) 22.

From an energy perspective, FIG. 1A shows a projectile 12 that is ready to be shot from a launcher (vertical bow) 14. In detail, the launcher 14 is configured to have a useable potential energy that can be converted into the kinetic energy of motion for the projectile 12. FIG. 1B on the other hand, shows the projectile 12 at its release point from the launcher 14, after the potential energy in the launcher (FIG. 1A) has been transferred to the projectile 12 as an internal mixture of potential energy and kinetic energy. In FIG. 1C, the payload 20 is shown after its separation from the projectile 12.

In terms of energy transfer, the separation of payload 20 from projectile 12 is caused when a portion of the kinetic energy in the projectile 12 (at launch, FIG. 1B) is pneumatically converted into potential energy of compression inside the projectile 12, and then reconverted into kinetic energy for the payload 20. With this reconverted kinetic energy, the velocity “v” of the payload 20 is increased sufficiently to separate the payload 20 from the projectile 12. Importantly, the payload 20 will substantially maintain the increased velocity “v”.

FIGS. 2 and 3, respectively, show two different embodiments for the present invention. In detail, FIG. 2 (with cross reference to FIGS. 4A-C) shows a projectile 12 which includes a proximal component 24 that defines an axis 26. For this embodiment of the present invention, a distal component 28 is positioned inside the proximal component 24 (see FIG. 4A). In another embodiment of the present invention, which is shown in FIG. 3, the distal component 28′ is positioned on the outside of the proximal component 24′. Both embodiments, respectively, include a nock 30 (30′) that is attached to the proximal component 24 (24′). Further, the embodiment for the device 12′ that is shown in FIG. 3 also includes a plurality of fletches 32 that are attached to the distal component 28′, and a plurality of fletches 34 that are attached to the proximal component 24′.

With reference to FIG. 4A, it will be appreciated that the proximal component 24 is an elongated tube which is formed with a lumen 36 that extends along the length of the proximal component 24. The lumen 36 has an open end 37, and it has an arresting ring 38 which is located proximate the open end 37. At the other end of the proximal component 24, the nock 30 is affixed to the proximal component 24 to establish a closed end for the lumen 36. FIG. 4A also shows that the distal component 28 of the projectile 12 is a cartridge 40 which holds a payload 20. For the embodiment of the projectile 12 shown in FIGS. 4A-C, the payload 20 is a shot cluster. Further, the cartridge 40 is shown to include a stabilizing ring 42 and a sealing ring 44 that together maintain an axial alignment for the cartridge 40 as it moves back and forth along the axis 26 inside the lumen 36 of the proximal component 24.

Still referring to FIG. 4A, with the distal component 28 (i.e. cartridge 40) positioned inside the lumen 36 of the proximal component 24, it will be appreciated that a compression chamber 46 is established between the cartridge 40 and the nock 30 of the projectile 12. Importantly, the sealing ring 44 establishes a substantially air-tight seal for the compression chamber 46. On the other hand, as evidenced by cross reference with FIGS. 4B and 4C, the cartridge 40 must be allowed to freely move back and forth inside the lumen 36 of the proximal component 24. Stated differently, it is essential to the operation of the present invention that the compression chamber 46 be dimensionally variable.

FIGS. 5A-C show another embodiment of the present invention wherein a compression chamber 48 is established in the lumen 36′ of the distal component 28′ of the projectile 12′. Specifically, for this embodiment, a sealing ring 50 is provided on the proximal component 24′ that interacts inside the lumen 36′ with the distal component 28′. With this interaction, a compression chamber 48 is established between the components 24′ and 28′. As with the compression chamber 46 for the embodiment of the projectile 12 (see FIGS. 4A-C), it is essential to the operation of the projectile 12′ of the present invention that the proximal component 24′ move freely relative to the distal component 28′, and that the compression chamber 48 thereby also be dimensionally variable.

In an operation of the present invention, a driving force 52 (represented by the arrows 52 in FIGS. 4A and 5A) is applied to the projectile 12 (12′) by way of the nock 30 (30′). This occurs during a transformation of the launcher 14 between the consecutive configurations shown in FIG. 1A and FIG. 1B. As shown in FIGS. 4A-C, the effect of this driving force 52 on the projectile 12 is at least three-fold. For one (see FIGS. 1A and 1B), the projectile 12 will be accelerated to a launch velocity “v” for release from the launcher 14. Simultaneously, in a second effect (see FIGS. 4A and 4B), the relatively unrestrained distal component 28 (i.e. cartridge 40) is caused to move forward more slowly (i.e. toward nock 30), against the resistance of gas in the compression chamber 46. Thirdly, gas in the compression chamber 46 is compressed by the relative movement of the distal component 28 (cartridge 40) as the dimensions of the chamber 46 become smaller (see FIG. 4B).

After the projectile 12 has been launched from the launcher 14 (see FIG. 1B), the driving force 52 no longer acts to accelerate the projectile 12. Also, the potential energy that was generated by compressing gas in the compression chamber 46 reaches its maximum. As gas in the compression chamber 46 is then allowed to expand, its potential energy is converted into a kinetic energy that is manifested by an increased velocity for the cartridge 40, and its payload 20. This increased velocity then causes the payload 20 to separate from the cartridge 40 and to continue along the flight path 16 (see FIG. 1C). At the same time, as gas in the compression chamber 46 expands, the conversion of potential energy into kinetic energy is also manifested as a decrease in the velocity of the proximal component 24. As intended for the present invention, this decrease in velocity of the proximal component 24 will result in the proximal component 24 being launched at a substantially lower velocity than the payload. A special case involves component 24 falling (generally vertically) to the ground along the separation path 22 (see FIG. 1C).

A similar operational scenario occurs for the embodiment of projectile 12′ as shown in FIGS. 5A-C. More specifically, as evidenced by a comparison of FIG. 5A with FIG. 5B, the driving force 52 acts on the nock 30′ to accelerate the projectile 12′. This also compresses gas in the compression chamber 48 in the distal component 28′. In this case, however, the payload 20′ is mounted directly on the distal component 28′ and, thus, both the payload 20′ and distal component 28′ are separated from the proximal component 24′. In the event, expanding gas in the compression chamber 48 acts to increase the velocity of the distal component 28′ (payload 20′) and to diminish the velocity of the proximal component 24′.

Referring now to FIG. 6A, a projectile assembly in accordance with the present invention is shown and is generally designated 54. In overview, FIG. 6A shows that the projectile assembly 54 includes a propulsion shaft 56 for receiving a cartridge 40 (shown in phantom) inside the shaft 56. In their structural cooperation with each other, the cartridge 40 and the propulsion shaft 56 together create the compression chamber 46 as generally disclosed above. FIGS. 6A and 6B both show that the projectile assembly 54 also includes a plug 58, and they indicate that the plug 58 is threaded into engagement with a ferrule 60 which is affixed to the distal end 62 of the propulsion shaft 56. Note: FIG. 6A is comparable to FIG. 1A, and FIG. 6B is comparable to FIG. 1B.

FIG. 7 shows that the external features of the cartridge 40 include a sabot 64 having a retention groove 66 that is affixed to its proximal end 68. Importantly, the retention groove 66 closes the proximal end 68 of the sabot 64. Further, it also includes a vent 70 that will establish fluid communication between the compression chamber 46 and the retention groove 66 when they are assembled with each other. It is also shown in FIG. 7 that the cartridge 40 includes a friction ring 72 which is positioned on the sabot 64. Preferably, the friction ring 72 is made of aluminum, and it is positioned on the sabot 64 to establish a “snug” fit that will typically create a radial pressure engagement between the sabot 64 and the friction ring 72 that is approximately five hundred psi. A slide ring assembly 74 is also provided for the cartridge 40. In particular, the slide ring assembly 74 is located distal to the friction ring 72, and it is provided to facilitate the interaction of the friction ring 72 with the propulsion shaft 56 during a launch of the payload 20 from the cartridge 40. The internal features of the cartridge 40, and the interaction of the cartridge 40 with the propulsion shaft 56 will be best appreciated with reference to FIG. 8.

FIG. 8 indicates that the particular payload 20 of interest for this adaptation of the present invention is a cluster of pellets 76. Preferably, the pellets 76 are made of either tungsten or steel, and they are dimensioned to be positioned and held inside the sabot 64. In particular, a retainer 78 is used to hold the pellets 76 inside the sabot 64 until the pellets 76 are to be separated from the cartridge 40, during a launch. In the embodiment shown in FIG. 8, the retainer 78 is a plurality of rings.

It is also shown in FIG. 8 that the cartridge 40 includes an O-ring assembly which includes both an outer ring 80 and an inner ring 82. For purposes of the present invention, the outer ring 80 is preferably made of polytetrafluoroethylene (PTFE); more commonly known as Teflon®, a brand name of the DuPont Company. Further, the outer ring 80 is formed with a diagonal split (not shown) that allows for very slight variations in contraction and expansion of the outer ring 80 during an operation of the projectile assembly 54. Also, as an integral part of the O-ring assembly, the inner ring 82 is preferably made of an elastomeric material (e.g. rubber) and it is positioned in the retention groove 66 with the outer ring 80, substantially as shown. Specifically, in this combination, the inner ring 82 is positioned to urge against the outer ring 80, to thereby force the outer ring 80 into direct contact with the inside of the propulsion shaft 56. As envisioned for the present invention, this contact between the outer ring 80 and the propulsion shaft 56 will create a substantially airtight seal for the compression chamber 46 at the proximal end 68 of cartridge 40.

It is also important to note that the vent 70 in the retention groove 66 is provided to equalize gas pressure in the compression chamber 46 with gas pressure against the O-ring assembly (i.e. outer ring 80 and inner ring 82). Specifically, this is done to prevent the rapid build-up of pressure in the gas compression chamber 46 during a launch from having an adverse effect on the O-ring assembly.

Still referring to FIG. 8, certain additional features of the present invention are also noteworthy. For one, at the distal end 62 of the propulsion shaft 56 it will be seen that the interaction of the plug 58 with the ferrule 60 creates an abutment 84. The purpose here is to establish a structure for arresting the cartridge 40 during a separation of the pellets 76 from the cartridge 40. Specifically, this happens when the sliding ring assembly 74 and friction ring 72 come into contact with the abutment 84 during a forward (distal) movement of the cartridge 40 through the propulsion shaft 56. It is further noted that the plug 58 can be easily disengaged (i.e. unthreaded) from the ferrule 60 to remove and replace cartridges 40 in the propulsion shaft 56.

As another feature of the present invention, at the proximal end 86 of the propulsion shaft 56, a pressure valve 88 (e.g. a Schrader valve) is provided. Preferably, the pressure valve 88 is mounted in the nock 30 as shown. The purpose here is to allow a pre-pressurization of the gas compression chamber 46 (e.g. 80 psig) prior to a launch of the projectile assembly 54. This will provide an initial resistance to gas compression at launch that will maximize the performance characteristics of the projectile assembly 54.

While the particular Two-Phase Projectile with a Proximal Compression Chamber as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims. 

What is claimed is:
 1. A man-powered system for pneumatically launching a pellet cluster which comprises: an elongated tubular-shaped cartridge formed with a lumen for holding the pellet cluster therein, wherein the cartridge has an open distal end and a closed proximal end; an elongated, cylindrical-shaped propulsion shaft formed with a lumen for receiving the cartridge therein for substantially free travel back and forth in the lumen of the shaft, wherein the shaft has an open distal end and a closed proximal end to establish a compression chamber in the lumen of the shaft between the proximal end of the cartridge and the proximal end of the shaft, wherein a volume of the compression chamber changes in response to movements of a cartridge in the shaft; and a launcher to impart a driving force on the proximal end of the shaft to launch the combination of cartridge and shaft, and to cause the cartridge to compress gas in the compression chamber for a subsequent expansion thereof to propel the cartridge forward in a distal direction through the lumen of the shaft, after launch, to separate the pellet cluster from the cartridge through the respective open ends of the cartridge and the propulsion shaft.
 2. A system as recited in claim 1 wherein the cartridge further comprises: an O-ring assembly positioned in a retention groove formed at the proximal end of the cartridge to establish a substantially airtight seal between the proximal end of the cartridge and an inner sidewall defining the lumen of the propulsion shaft; a plurality of retainer tubes positioned in the lumen of the cartridge at the distal end thereof to maintain the pellet cluster in the lumen of the cartridge prior to launch; and a friction collar positioned on an outer surface of the cartridge for a snug engagement therewith to generate friction forces against the cartridge to retard movement of the cartridge for separation of the pellet cluster from the cartridge.
 3. A system as recited in claim 2 wherein the retention groove is formed with at least one vent hole to establish fluid communication for equalizing pressure between the retention groove and the compression chamber, and wherein the O-ring assembly comprises: an outer ring positioned in the retention groove for contact with an inner surface of the propulsion shaft, wherein the inner surface defines the lumen of the propulsion shaft; and an inner ring positioned in the retention groove to produce a force against the outer ring to urge the outer ring into contact against the inner surface of the propulsion shaft.
 4. A system as recited in claim 3 wherein the inner ring is made of rubber and the outer ring is made of polytetrafluoroethylene (PTFE), and further wherein the outer ring is formed with a diagonal split to permit contraction and expansion of the outer ring.
 5. A system as recited in claim 2 wherein the friction collar is made of aluminum and exerts a radial pressure against the cartridge of approximately 500 psi.
 6. A system as recited in claim 2 further comprising a slide ring assembly positioned on the outer surface of the cartridge distal to the friction collar to mitigate impact forces against the friction collar at the launch of the pellet cluster.
 7. A system as recited in claim 1 wherein the propulsion shaft further comprises: a pressure valve positioned at the proximal end of the propulsion shaft for use in pressurizing the compression chamber to a predetermined gauge pressure (psig) prior to imparting the driving force against the shaft; a ferrule attached to the distal end of the propulsion shaft, wherein the ferrule has a threaded extension projecting in a distal direction from the distal end of the shaft; and a plug joined in a threaded engagement with the ferrule to create an abutment around the open distal end of the propulsion shaft to establish a distal limit for movement of the cartridge in the lumen of the shaft.
 8. A system as recited in claim 7 wherein the pressure valve is mounted in a nock, and the nock is affixed to the proximal end of the propulsion shaft for operational interaction with the launcher.
 9. A system as recited in claim 1 wherein pellets in the pellet cluster are made of a material selected from the group consisting of tungsten and steel.
 10. A cartridge for use with a man-powered launcher which comprises: a pellet cluster; an elongated tubular-shaped sabot formed with a lumen for holding the pellet cluster therein, wherein the sabot has an open distal end and a closed proximal end with a retention groove formed at the proximal end of the sabot; an O-ring assembly positioned in the retention groove; a plurality of retainers positioned in the lumen of the cartridge at the distal end thereof to maintain the pellet cluster in the lumen of the cartridge prior to launch; and a friction collar positioned on an outer surface of the sabot.
 11. A cartridge as recited in claim 10 wherein the cartridge is dimensioned to interact with an elongated, cylindrical-shaped propulsion shaft formed with a lumen for receiving the cartridge therein for substantially free travel back and forth in the lumen of the shaft, wherein the shaft has an open distal end and a closed proximal end to establish a compression chamber in the lumen of the shaft between the proximal end of the cartridge and the proximal end of the shaft, wherein a volume of the compression chamber changes in response to movements of a cartridge in the shaft.
 12. A cartridge as recited in claim 11 wherein the combination of cartridge and propulsion shaft is mounted on a launcher, and the launcher is configured to impart a driving force on the proximal end of the shaft to launch the combination of cartridge and shaft, and to cause the cartridge to compress gas in the compression chamber for a subsequent expansion thereof to propel the cartridge forward in a distal direction through the lumen of the shaft to separate the pellet cluster from the cartridge through the respective open ends of the cartridge and the propulsion shaft after launch.
 13. A cartridge as recited in claim 12 wherein the retention groove on the sabot is formed with at least one vent hole to establish fluid communication for equalizing pressure between the retention groove and the compression chamber, and wherein the O-ring assembly comprises: an outer ring positioned in the retention groove for contact with an inner surface of the propulsion shaft, wherein the inner surface defines the lumen of the propulsion shaft; and an inner ring positioned in the retention groove to produce a force against the outer ring to urge the outer ring into contact against the inner surface of the propulsion shaft.
 14. A cartridge as recited in claim 13 wherein the inner ring is made of rubber and the outer ring is made of polytetrafluoroethylene (PTFE), and further wherein the outer ring is formed with a diagonal split to permit contraction and expansion of the outer ring.
 15. A cartridge as recited in claim 12 wherein the propulsion shaft further comprises: a pressure valve positioned at the proximal end of the propulsion shaft for use in pressurizing the compression chamber to a predetermined gauge pressure (psig) prior to imparting the driving force against the shaft; a ferrule attached to the distal end of the propulsion shaft, wherein the ferrule has a threaded extension projecting in a distal direction from the distal end of the shaft; and a plug joined in a threaded engagement with the ferrule to create an abutment around the open distal end of the propulsion shaft to establish a distal limit for movement of the cartridge in the lumen of the shaft.
 16. A cartridge as recited in claim 12 wherein the friction collar is made of aluminum and is dimensioned for a snug engagement with the sabot to exert a radial pressure against the cartridge of approximately 500 psi for generating friction forces to retard movement of the sabot for separation of the pellet cluster from the sabot, and wherein the cartridge further comprises a slide ring assembly positioned on the outer surface of the cartridge distal to the friction collar to mitigate impact forces against the friction collar at the launch of the pellet cluster.
 17. A propulsion shaft for use with a man-powered launcher which comprises: an elongated, cylindrical-shaped tube formed with a lumen for receiving a cartridge therein for substantially free travel back and forth in the lumen of the tube, wherein the tube has an open distal end and a closed proximal end to establish a compression chamber in the lumen of the tube between the proximal end of the cartridge and the proximal end of the tube, wherein a volume of the compression chamber changes in response to movements of the cartridge in the tube; and a pressure valve positioned at the proximal end of the tube for use in pressurizing the compression chamber to a predetermined gauge pressure (psig).
 18. A propulsion shaft as recited in claim 17 further comprising: a ferrule attached to the distal end of the tube, wherein the ferrule has a threaded extension projecting in a distal direction from the distal end of the tube; and a plug joined in a threaded engagement with the ferrule to create an abutment around the open distal end of the tube to establish a distal limit for movement of the cartridge in the lumen of the tube.
 19. A propulsion shaft as recited in claim 17 wherein the pressure valve is mounted in a nock, and the nock is affixed to the proximal end of the tube for operational interaction with the launcher.
 20. A propulsion shaft as recited in claim 17 wherein the cartridge holds a pellet cluster, and pellets in the pellet cluster are made of a material selected from the group consisting of tungsten and steel. 